The invention relates to a system for performing an assay of a cell sample to provide an accurate quantitative analysis of a characteristic of the cells which have been sampled. More particularly, the invention is directed to a system which receives images of stained cells and enhances the cell images prior to further processing to determine an amount of oncogene protein product in the cells of a cell sample.
One of the problems which faces pathologists in their clinical practice is that of determining whether a cell sample taken from a patient during a biopsy procedure or the like is benign, malignant and if malignant the classification or cell type. Although a surgeon may have a good intuition about the type of tissue mass which he has removed, nevertheless he must confirm his preliminary diagnosis with a histological examination of the cell sample removed from the patient. The histological examination entails cell staining procedures which allow the morphological features of the cells to be seen relatively easily in a light microscope. A pathologist after having examined the stained cell sample, makes a qualitative determination of the state of the tissue or the patient from whom the sample was removed and reaches a conclusion as to whether the patient is normal, or has a premalignant condition which might place him at risk of a malignancy in the future or has cancer. While this diagnostic method has provided some degree of predictability in the past, it is somewhat lacking in scientific rigor since it is heavily reliant on the subjective judgement of the pathologist. In addition, it is sometimes difficult for the practitioner to determine the stage which the tumor has reached. Such a determination often allows the clinician to select a particular treatment by balancing the tumor's resistance to therapy with the potential harm resulting from the selected therapy.
Attempts have been made to automate the cellular examination process. In U.S. Pat. No. 4,741,043 to Bacus for Method and Apparatus for Image Analyses of Biological Specimens, an automated method and a system for measuring the DNA of cells are disclosed which employ differential staining of the DNA in cell nuclei with a Feulgen Azure A stain and image processing.
U.S. application Ser. No. 315,289, filed Feb. 24, 1989, now U.S. Pat. No. 5,086,476 for Method and Apparatus for Determining a Proliferation Index of a Cell Sample to Bacus, assigned to the instant assignee, discloses a system for determining the proliferation index of cells by microscopic examination of cell samples which have been stained with a proliferation substance stain and a nuclear stain. The system includes a computer coupled to a pair of monochrome television cameras, which receive optically filtered images of the magnified cell images, and an image processor. The system computes the proliferation index from the optical characteristics of the stained cell sample.
Recently certain genes have been discovered that appear to contribute to the onset and growth of cancers. These genes, known as oncogenes and proto-oncogenes, also may contribute to the growth and development of human beings in the early stages of their lives. Ongoing research has found that certain of these oncogenes seem to be related to specific cancers. One of them, the neu HER-2 proto-oncogene, appears to be related to human breast and ovarian cancers. It has also recently been found that neu HER-2 proto-oncogenes and the oncogene protein product that is expressed from neu HER-2 appear, when in elevated amounts, to be correlated with the virulence of the cancer, Slamon D.J. et al., "Studies of the HER-2/neu Proto-oncogene in Human Breast and Ovarian Cancer," Science Vol. 244, pp. 707-712, May 12, 1989. Thus the ability to quantitate the amount of neu HER-2 proto-oncogene and/or its oncogene protein product will allow a clinician to better predict the likelihood of a patient surviving her cancer after completing a selected treatment regimen. By having such information, the clinician will also be better able to select an appropriate treatment regimen to maximize the patient's likelihood of survival.
There would appear to be two ways in which the measurement could be made. The number or amount of neu HER-2 proto-oncogene could be determined in a cell sample using gene probes, which would be expensive and inefficient. Alternatively, the amount of oncogene protein product in the cytoplasm could be measured. While the second choice appears to be more attractive, there are a number of problems encountered with such an approach which prevent easy measurement. The typical tissue specimen biopsied from human breast or ovarian tissue is frozen and then sectioned for microscopic examination. Pathologists favor being able to inspect visually the frozen sections since the portions having malignant cells may be scattered throughout the tissue specimen. It is also difficult to easily determine the locations of cell boundaries in a crowded field because the cancer cells have irregular boundaries. In addition, the monoclonal antibody based stains for visualizing the oncogene protein product work best on frozen sections, as opposed to other types of prepared cell samples. Unfortunately, the sectioned tissue suffers from the problem that while a number of whole cells are present in the section, a number of fractional portions of cells are also present, preventing assaying simply by counting of the cells in an image field of a microscope. It is important to know the sum total of cells being examined because the assay of oncogene protein product is on the basis of the amount of oncogene protein product per cell.
What is needed is a method and apparatus for automatically and quickly assaying the amount of oncogene protein product in the cells of frozen sectioned tissues taken from a human patient.